Related papers: Transitional Disks as Signposts of Young, Multipla…
Transition disks, with inner regions depleted in dust and gas, could represent later stages of protoplanetary disk evolution when newly-formed planets are emerging. The PDS 70 system has attracted particular interest because of the presence…
Context.Transition disks are believed to be the final stages of protoplanetary disks, during which a forming planetary system or photoevaporation processes open a gap in the inner disk, drastically changing the disk structure. From…
Nearly all young stars are initially surrounded by `protoplanetary' discs of gas and dust, and in the case of single stars at least 30\% of these discs go on to form planets. The process of protoplanetary disc formation can result in…
Planets form in young circumstellar disks called protoplanetary disks. However, it is still difficult to catch planet formation in-situ. Nevertheless, from recent ALMA/SPHERE data, encouraging evidence of the direct and indirect presence of…
I describe new constraints on the lifetimes and morphologies of transitional protoplanetary disks from observations of 1--10 Myr old stars with the \textit{Spitzer Space Telescope}. New Spitzer results clearly show evidence for two kinds of…
Turbulent coagulation in protoplanetary disks is known to operate on timescale far shorter than the lifetime of the disk. In the absence of mechanisms that replenish the small dust grain population, protoplanetary disks would rapidly lose…
The environment of a binary star system may contain two circumstellar disks, one orbiting each of the stars, and a circumbinary disk orbiting about the entire binary. The disk structure and evolution are modified by the presence of the…
The majority of stars are part of gravitationally bound stellar systems, such as binaries. Observations of protobinary systems constrain the conditions that lead to stellar multiplicity and subsequent orbital evolution. We report…
Young stars are surrounded by a circumstellar disk of gas and dust, within which planet formation can occur. Gravitational forces in multiple star systems can disrupt the disk. Theoretical models predict that if the disk is misaligned with…
Isotopic properties of meteorites provide evidence that multiple dust trap or pressure bumps had to form and persist in the inner Solar System on a timescale of millions of years. The formation of a pressure bump at the outer edge of the…
Observations of structure in circumstellar debris discs provide circumstantial evidence for the presence of massive planets at large (several tens of au) orbital radii, where the timescale for planet formation via core accretion is…
Complex structures, including sharp edges, rings and gaps, have been commonly observed in protoplanetary disks with or without planetary candidates. Here we consider the possibility that they are the intrinsic consequences of angular…
Recent observations have suggested that circumstellar disks may commonly form around young stellar objects. Although the formation of circumstellar disks can be a natural result of the conservation of angular momentum in the parent cloud,…
The discovery of giant planets in wide orbits represents a major challenge for planet formation theory. In the standard core accretion paradigm planets are expected to form at radial distances $\lesssim 20$ au in order to form massive cores…
The physical and chemical conditions in young protoplanetary disks set the boundary conditions for planet formation. Although the dust in disks is relatively easily detected as a far-IR photometric ``excess'' over the expected photospheric…
Accretion disks are observed in young stars, cataclysmic variables, binary X-ray sources et al. Accretion disk theory was first developed as a theory with the local heat balance, where the whole energy produced by a viscous heating was…
During their formative stages, giant planets are fed by infalling material sourced from the background circumstellar disk. Due to conservation of angular momentum, the incoming gas and dust collects into a circumplanetary disk that…
The observation of massive exoplanets at large separation from their host star, like in the HR 8799 system, challenges theories of planet formation. A possible formation mechanism involves the fragmentation of massive self-gravitating discs…
Aerodynamic theory predicts that dust grains in protoplanetary disks will drift radially inward on comparatively short timescales. In this context, it has long been known that the presence of a gap opened by a planet can alter the dust…
Intermediate mass planets, from Super-Earth to Neptune-sized bodies, are the most common type of planets in the galaxy. The prevailing theory of planet formation, core-accretion, predicts significantly fewer intermediate-mass giant planets…